KQI changes with the evolutional network.

a-f, Simplified evolutional network on informetrics field from 1990 to 2021. Nodes represent the articles and edges represent the citation relationships. The nodes at the right cite the nodes at the left, in chronological order from left to right. The networks correspond to snapshots in 1990, 1995, 2000, 2005, 2010, and 2020 respectively. Additional 20 nodes (green) are marked to specifically compare with changes in metrics. g-i, KQI, PageRank, and citation variation of typical nodes. The gradient color corresponds to the evolution time of a-f. F, I, N, Q represent articles that gradually drifted away from the research center, with reduced KQI, reduced PageRank, and smooth citations. E, J represent articles that are little-known but enlightening, with considerable KQI and few citations. A, C, D shows that PageRank of articles whose citations do not continue to grow decreases, while the KQI stays high. B, G shows that increasing citations maintain PageRank. D, E, M shows that KQI reflects the change of research hotspots in the network.